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Ebola case in the US highlights risk to other nations

By Debora MacKenzie

The first case of Ebola developing in the US was in Dallas, Texas

(Image: Mike Stone/Getty)

For the first time, someone has developed Ebola outside the tropics. The man was infected in Liberia, and fell ill after flying to Dallas, Texas. He is now hospitalised, isolated and in critical condition.

The man developed symptoms including fever on 24 September in Dallas and went to a hospital in the area on 26 September but was sent home, despite the fact that he had flown in from Monrovia, the capital of Liberia and the epicentre of the Ebola epidemic, six days earlier.

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He went back with worsening symptoms two days later, and was isolated. It took another two days to confirm the case as Ebola.

Ebola infection takes two to 21 days to cause symptoms. People are not thought to be able to transmit the infection until after symptoms have developed, meaning someone can travel while appearing healthy, then fall ill in a country where the disease may not immediately be recognised.

“The Dallas hospital where the patient with Ebola is now admitted has been planning for a possible admission for some time”, and had met to discuss measures just the previous week, says Thomas Inglesby, an infectious disease researcher at the University of Pittsburgh, Pennsylvania. But if a doctor or nurse doesn’t ask someone where they are from, then they won’t be prompted to think about Ebola, he says. He hopes this event will heighten sensitivities.

Alessandro Vespignani of Northeastern University in Boston and his colleagues have rated the risk of different countries around the world importing cases of Ebola. After Ghana and Gambia, the UK has the third highest risk globally because of the large number of people and flights from the epidemic region to London.

In September, the risk for importing a case to the UK was around 25 per cent, and slightly less for the US.

On the lookout

Doctors and hospitals in the UK have been told to be on the lookout for possible cases, says Peter Piot of the London School of Hygiene and Tropical Medicine.

Efforts are being made to keep sick people off planes. But Heinz Feldmann, who studies Ebola at the US National Institute of Allergy and Infectious Diseases, said two weeks ago on returning from Liberia that workers taking people’s temperatures before allowing them into Monrovia airport seemed not to know how to do their jobs. Once inside the airport, he said, passengers were crowded together, increasing the chance that anyone with symptoms might pass on the infection.

Once such cases are diagnosed in wealthy countries, the problem becomes stopping its spread.

“I have no doubt that we’ll stop this in its tracks in the US,” Tom Frieden, head of the CDC, said yesterday in a briefing on the Dallas case.

David Heymann of the London School of Hygiene and Tropical Medicine agrees. He says that as long as contacts of sick people are traced and isolated, this should be straightforward. Heymann helped organise the global effort that used such measures to halt the SARS virus in 2003.

But unless the outbreak in Africa is brought under control, the risk to other countries will continue to climb, says Vespignani. “Most countries in the world approach a probability of 100 per cent of importing a case in December if the epidemic continues to grow at its current rate,” he says. He fears some countries may not be able to contain subsequent transmission, further worsening the situation.